I. Field of the Invention
The present invention relates to a method of solvating metal ions in an aromatic organic liquid.
II. Description of the Related Art
It is well known that the solubility of metal ions in an aromatic organic liquid is limited. Aromatic organic liquids are typically hostile for dissolving metal salts. Various techniques have been employed for solvating an inorganic metal salt in an aromatic organic liquid. These methods, however, have proven inadequate for certain applications, particularly those where the optical characteristics of the solvated metal ions are of importance. To date, these known techniques have solvated substantially less than ten percent (10%)xe2x80x94e.g., about one percent (1%)xe2x80x94of the metal ions by weight in the aromatic organic liquid. Using these methods, the solvated metal ions to date have been turbidxe2x80x94e.g., the particles are not homogenously solvated, but are suspended.
The formation of metal salts using transitional metals soluble in an organic hydrocarbon media is known. To date, these solutions have been used in paints, for example, to accelerate drying. The known solutions are typically heterogeneous, as well as optically opaque, thereby scattering light when employed in certain applications. Consequently, homogeneity and/or optical transparency have not become established requirements for these known solutions.
The present invention provides a method for solvating metal ions in an aromatic organic liquid. More particularly, the method promotes solvating one or more metals, such as Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Lu, In, Gd, Pb and Yb, for example, in an aromatic organic liquid. By this method, at least ten percent (10%) by weight of metal ions is solvated in the aromatic organic liquid. Using the method of the present invention, the solvated metal ions may be characterized as homogenous. Moreover, depending on the metal selected, the solvated metal ions may also be optically transparent (e.g., does not substantially scatter light), as well as supporting a solution capable of fluorescence at one or more wavelengths, for example, in response to receiving radiation.
In accordance with the present invention, a reagent is employed for increasing the concentration of a metal ion(s) solvated in an aromatic organic liquid. The reagent may comprise a carboxylate having less than or equal to 8 carbon atoms. An aliphatic carboxylate may be employed, for example, as the reagent.
In an embodiment, an aqueous solution comprising a metal salt is added to an organic liquid comprising an ammonium salt formed from an organic acid reagent. The organic acid reagent increases the amount of metal ions solvated. The stoichiometry of the constituents of the aqueous solution and organic liquid is selected such that this step produces a metal organic salt.
In another embodiment of the present invention, a complexing agent may be used in solvating metal ions. The complexing agent increases the stability of an organic phase created as a result of solvating the metal ions. Here, the complexing agent is added to the organic liquid prior to introducing the aqueous solution comprising the metal salt. Various metal complexing agents may be employed in this regard, such as tri-alkyl phosphine oxide and/or tri-butyl phosphine oxide, for example.